1. Technical Field
Apparatuses and methods consistent with the exemplary embodiments relate to an apparatus and method for supplying power. More particularly, the exemplary embodiments relate to an apparatus and method for supplying power, in which parts of the power supply device are protected and performance of an audio system which varies in load is not deteriorated, even though the audio system is overloaded.
2. Description of the Related Art
A general power supply for an audio system outputs a constant voltage regardless of a load. Thus, under a peak load condition of the audio system, the power supply becomes overloaded several times higher than rated power. If such a condition lasts, heat generated in parts of the power supply for the audio system becomes serious, thereby causing a defect, resulting in product liability (PL).
FIG. 1 shows a related art flyback type power supply 10 of an audio system. As shown in FIG. 1, when alternating current (AC) power is applied via a bridge rectifier circuit 11, a switching element MOSFET SW1 starts a switching operation by a start-up circuit of a pulse width modulation (PWM) integrated circuit (IC) 12, and therefore the switching operation causes a primary transformer 13 and a secondary transformer 14 to apply a voltage VCC, thereby normally operating the PWM IC 12. A secondary output voltage of the primary transformer 13 is supplied as a signal to the PWM IC 12 through a feedback circuit 15 which includes a shunt regulator, an output dividing resistor R2 and a photo-coupler, thereby controlling the switching element SW1 to switch on/off. The output Vamp of the primary transformer 13 is started as above, and this output undergoes regulation through feedback control. The regulation for the output voltage through the feedback control is performed as follows.
In response a voltage applied to both ends of the output dividing resistor R2 being higher than a reference voltage Ref of the shunt regulator, the shunt regulator is turned on and electric current flows in a primary side of the photo-coupler. In result, a signal is transmitted even to a secondary side of the photo-coupler, and therefore the electric current flows in the secondary side, thereby varying a switching duty of the PWM IC 12.
Referring to FIG. 2, the power supply 10 is regulated to maintain a constant voltage (CV) through the feedback control even though the load current increases or decreases. Also, a protection circuit may be designed to operate to shut down (i.e., protect) the output voltage when the load continuously increases and reaches an overload state.
For example, in the case of the power supply for the audio system, maximum peak power has to be properly supplied with regard to peak music power output (PMPO). Since the output voltage is constantly supplied with regard to even a sound source of which the peak music power output is continued, it is possible to continuously supply power several times higher than rated output. As a result, abnormal power higher than the rated output is continuously output, and therefore semiconductor and magnetic parts in the power supply 10 are overheated and cause a serious problem of a defect resulting in product liability (PL).
To cope with the peak output of such an audio system, the capacities of a transformer and an input/output electrolytic capacitor may be designed to be overspecialized, but this causes a problem of rise in price.